Thuridilla virgata
(Bergh, 1888)

Superfamily: ELYSIOIDEA
Family: Elysiidae


Known only from the Indian Ocean [Mauritius, Madagascar, South Africa, Tanzania]


Pereybere, Mauritius, Indian Ocean, October 2002, Depth: 10m, Size: approx 25mm. Photos: Marina Poddubetskaia

The body is a pale bluish white with a series of broad black longitudinal bands, of irregular width and length, on the parapodia. The head is essentially black with a Y-shaped bluish white band running along the medio-dorsal line, a branch going to each rhinophore. The rhinophores, or at least the upper two-thirds, area golden yellow. This species seems to be endemic to the Indian Ocean. Originally described from Mauritius, it has also been reported from South Africa, Madagascar and Tanzania.

• Bergh, L.S.R. (1888) Malacologische Untersuchungen. In: C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate. Band 2, Heft 16a: 755-814. (Pls. 77-81)
• Gosliner, T.M. (1995) The genus Thuridilla (Opisthobranchia: Elysiidae) from the tropical Indo-Pacific, with a revision of the phylogeny and systematics of the Elysiidae. Proceedings of the Californian Academy of Sciences 49(1): 1-54.

Authorship details
Rudman, W.B., 2002 (October 30) Thuridilla virgata (Bergh, 1888). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

Thuridilla virgata from Reunion Island

February 7, 2008
From: Hugues Flodrops

Concerning message #13238:

Dear Bill,
Happy New Year 2008 and thanks for your forum. I've noticed that there was few record of Thuridilla virgata. I confirm your impression that it's an Indian Ocean endemic species with this record. It's a second record from Reunion Island (First one was found by Emmanuel Eby at Saint-Leu). Reunion Island:

Locality: Grande ANse, 2 mètres, Reunion Island, Indian Ocean, 25 December 2007, Muddy. Length: 25 mm. Photographer: Hugues Flodrops.

Best regards.

Flodrops, H., 2008 (Feb 7) Thuridilla virgata from Reunion Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Hugues,

Thanks for another record of this species. You raise an interesting quandary when you say your find confirms this species is an Indian Ocean endemic. Logically you can't prove that it is absent from the rest of the world by showing it is present in one part. Which raises the question of how to you prove an animal is endemic to a certain area? How many times do you have to 'not find' it elsewhere before you can say it is really absent?

There is no easy answer to this. It is easier for land animals because most of them don't seem to travel far, or if they do it is in a fairly regular way so a few years regular sampling can usually give you a good idea of what is present and what is absent. In the marine environment though where animals are often distributed in water currents as larvae, we can find major variations in distributions over many years. And then again there is the problem of poor sampling in many parts of the world. As we have seen on the Forum, an animal described from Sri Lanka 150 years ago and never seen again can suddenly be found in Thailand, or a species apparently endemic to part of the east Atlantic will be found on the east coast of Nth America.

T. virgata seems as though it may be endemic to the western Indian Ocean but as soon as we say it definitely is it will turn up in Thailand or Western Australia or even in the Pacific.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Feb 7). Comment on Thuridilla virgata from Reunion Island by Hugues Flodrops. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thuridilla virgata in Mozambique

February 28, 2005
From: Riaan Marx

Hi Dr. Rudman,
Here is a picture of Thuridilla virgata (I think). It seems to me these critters can pull the old tortoise trick as well...

Locality: Ponta Malongane (Creche reef), Mozambique, Indian Ocean. Depth: 12 metres. Length: 15-20 mm. 8 February 2005' Sandy patches on rocky reef. Photographer: Riaan Marx

Kind regards
Riaan Marx.

Marx, R., 2005 (Feb 28) Thuridilla virgata in Mozambique. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Riaan,
There are only 5-6 records of T. virgata since it was described in 1888, so this is a valuable addition. If by the 'old tortoise trick' you are referring to it pulling its head, yes all the elysiids can do that. Perhaps it might protect the head, but since they are soft bodied its not much protection.
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Feb 28). Comment on Thuridilla virgata in Mozambique by Riaan Marx. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thuridilla virgata from Mauritius

November 1, 2002
From: Marina Poddubetskaia

Dear Bill,
In Mauritius I saw many specimens of this little sacoglossan in several sites. It seems to be quite common there. I think, it is a Thuridilla species but I can't recognize which one. It looks a little like Thuridilla gracilis, but:
- the rhinophores are orange-yellow and not just tipped with orange
- the foot and the head aren't edged with orange (I looked at it closer in a tank)
- the whitish mark on the head is Y-shaped and not T-shaped

Have you any idea which species is it?

Location: Pereybere, Mauritius, Indian Ocean, Site: L'aquarium de Pereybere
Upper and Lower Left: October 15, 2002, Depth: 10m, Size: 15-17mm
Lower Right: animal found under a dead coral, October 12, 2002, Depth: 10m, Size: 12-13mm. Photos: Marina Poddubetskaia - Nembro website

Thank you in advance.
Best wishes,

Poddubetskaia, M., 2002 (Nov 1) Thuridilla virgata from Mauritius. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Marina,
This is Thuridilla virgata. A nice addition to the Forum. It is only known from the Indian Ocean, and was first described from specimens collected in Mauritius.
Best wishes,
Bil Rudman

Rudman, W.B., 2002 (Nov 1). Comment on Thuridilla virgata from Mauritius by Marina Poddubetskaia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from